The present invention relates to a Video signal optical transmission system which transmits the video signal from a transmitting part to a receiving part through an optical fiber transmission path.
In an optical fiber transmission system, for a community access television (CATV) system or the like, video signals are transmitted after being frequency modulated. This technique avoids the effect of wave distortion or the like which might result from insufficient linearity of a semiconductor laser used to transmit the video signal on the optical fiber.
FIG. 1 is a schematic block diagram of such a conventional optical transmission system. In FIG. 1, a frequency modulator 1b in a transmitting part 1 frequency modulates a composite video signal transmitted by video equipment such as a video camera and a video tape recorder (VTR). An electro-optical (E/O) converter 1c converts the resulting frequency modulated signal into an optical signal, and an optical fiber 2, serving as a signal transmission path, transmits the optical signal to a receiving part 3.
An opto-electrical (O/E) converter 3a in a receiving part 3 converts the optical signal transmitted through the optical fiber 2 to an electrical signal. A frequency demodulator 3b demodulates the resulting frequency modulated signal to obtain a composite video signal. The composite video signal is transmitted via a coaxial line or the like (not shown) to a terminal or the like where it is used for displaying a video or recording a picture in a video tape recorder (VTR).
As described above, in transmitting a video signal it has been necessary to provide a frequency modulator 1b on the transmitting side and a corresponding dedicated frequency demodulator 3b on the receiving side, the added circuitry raising the cost of the system.